Update configure.ac to not use AC_TRY_COMPILE

================================================================================
Running autoconf...
configure.ac:465: warning: The macro `AC_TRY_COMPILE' is obsolete.
configure.ac:465: You should run autoupdate.
../../lib/autoconf/general.m4:2615: AC_TRY_COMPILE is expanded from...
../../lib/m4sugar/m4sh.m4:643: AS_IF is expanded from...
../../lib/autoconf/general.m4:2046: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2059: AC_CACHE_CHECK is expanded from...
../../lib/m4sugar/m4sh.m4:643: AS_IF is expanded from...
../../lib/autoconf/general.m4:2046: AC_CACHE_VAL is expanded from...
configure.ac:465: the top level
================================================================================

This produces the same test and results, without the warning.

Signed-off-by: Bryan Hundven <bryanhundven@gmail.com>
Merge pull request #19 from bhundven/master

Update configure.ac to not use AC_TRY_COMPILE